The present invention relates generally to a method and apparatus for unwinding a filament from a spool, and more particularly to an improved method and apparatus for a fully automatic spool filament impeller for use in vegetation trimmers and other applications benefiting from continuously adjusting filament extension to maintain a constant length.
There are three types of cutting heads for vegetation trimmers that use filaments for cutting the vegetation: manual, semiautomatic, and automatic. With manual and semiautomatic vegetation trimmers, the operator must monitor filament wear. When the filament becomes too short to be effective, the filament must be extended or replaced by the operator. Today most filament vegetation trimmers come equipped with manual or semiautomatic cutting heads.
An operator using a manual vegetation trimmer is responsible for monitoring the filament length and adjusting its length as needed to maintain effective cutting. The operator must stop the trimmer to a) manually extend the filament; or b) discard the stub length of old filament, install a new length of filament and manually extend the filament to the correct starting length. Using manual vegetation trimmers also means taking valuable time to adjust the filament to the correct cutting length.
If the operator is using a semiautomatic vegetation trimmer, the operator is also responsible for monitoring the filament length and adjusting the filament length to maintain the appropriate cutting length. When the operator detects that the filament needs adjustment, the operator must take the time to directly activate a mechanism to extend the filament. For these semiautomatic systems it is not always necessary to stop the trimmer before making a filament length adjustment. If the filament needs replacement then the trimmer must be stopped before replacing the filament on the spool. Using semiautomatic vegetation trimmers also means interrupting the trimming operation and taking valuable time to adjust the filament to the correct cutting length. Some filament is wasted when only a portion of the length needs replacement and an excess of what is needed is automatically released. In addition, because semi-automation means a greater number of active parts, the initial purchase price for the device is higher as is the likelihood of having to repair or replace parts for proper operation.
With an automatic vegetation trimmer, the operator does not need to monitor the filament length. Without operator intervention, an automatic vegetation trimmer cutting head periodically extends a new fixed length of filament. Filament is deployed from an internal spool through a hole in a housing upon an automatic mechanism""s periodic (a) release of a spool brake or (b) indexing of the spool by advancing it to its next predefined position.
In some automated trimmers, a counterweight counterbalances the filament tension and the automatic mechanism is activated by the mechanism""s detection of reduced filament tension. During operation, other automatic vegetation trimmers activate the automatic mechanism upon detecting the filament spool""s increased rotational speed beyond some preset range.
Cutting swath size fluctuations are inherent in automatic and semiautomatic vegetation trimmers whose automatic feeding mechanisms deliver a fixed length of filament with each activation. Some filament is wasted when only a portion of the length needs replacement and the automated mechanism releases an excess of what is actually needed. If the extended filament is too long, the trimmer is overloaded and its motor may fail prematurely. Electric trimmers are especially sensitive to overloading. Motor overloading due to the stress of overlong extended filaments is a problem common to manual, semiautomatic, and automatic vegetation trimmers.
Ideally, to conserve filament, only the tip of the extended filament should strike the vegetation. While the automatic or semiautomatic vegetation trimmer is engaged in trimming vegetation, each time the size of the cutting swath suddenly increases by some fixed automatically dispensed length of filament, a segment at the distal end of the extended filament impacts the vegetation. While operating with an increased cutting swath, more than the tip of the extended filament strikes the vegetation. The extended filament segment making contact with the vegetation receives impact damage throughout its length. This impact damage results in premature filament failure and the periodic loss of whole segments of filament.
An overly long filament segment is likely to fail at a point recessed back from the tip. The result is the periodic loss of whole segments of filament rather than the gradual wear of material from the tip. To prevent excessive length, some prior trimmers are equipped with a cutoff blade positioned to cut off excess filament. Not only does this waste filament, but the severed flying tip is annoying or even dangerous.
Significant wear accumulates before the activation threshold of the automatic filament feeding mechanism is exceeded. Automatic and semiautomatic vegetation trimmers operate in a cycle of gradual declines and sudden increases in the cutting swath. This cycle results in wasted filament and difficulty in maintaining refined control of the cutting swath which may result in wasteful repetitive operator motion or inadvertent cuttings.
Automation and semi-automation mechanisms typically found in vegetation trimmers mean a greater number of active parts and corresponding greater complexity and weight. Easily maneuvered weight is important to users that frequently operate the device for long periods as well as infrequent users who may lack physical conditioning to wield the heavier trimmers for even short periods such as would be required in dressing a relatively small vegetation area. The initial purchase price for automatic and semiautomatic devices with their greater number of parts and complexity is higher as is the likelihood of having to repair or replace parts for proper operation. Most automatic and semi-automatic cutting heads must be disassembled for reloading. The casual occasional users and inexperienced users must consult a manual or waste time on trial and error efforts. Reloading seems to be particularly complex.
An ideal vegetation trimmer would (a) minimize wasting the operator""s time in non-trimming operation, (b) conserve filament, (c) maintain a consistent and predictable cutting perimeter, (d) have a simplified design to reduce initial purchase cost and maintenance cost, (e) be lightweight, and (f) be simple to operate and reload. The above inventions fail to meet these individual and combined goals for an ideal vegetation trimmer. For the foregoing reasons, there is a need for a fully automatic vegetation trimmer which does not waste filament and which is simple, easy to use, consistent, reliable, and inexpensive.
The present invention is directed to an improved method and apparatus for a fully automatic spool filament impeller for use in vegetation trimmers and other applications benefiting from continuously adjusting a rotating filament centrifugally extended such that a constant extended filament length is maintained. The present invention satisfies the needs identified above for a device that (a) minimizes wasting the operator""s time in non-trimming operation, (b) conserves filament, (c) maintains a consistent and predictable cutting perimeter, (d) has a simplified design to reduce initial purchase cost and maintenance cost, (e) is lightweight, and (f) is simple to operate and reload.
The present invention comprises a fully automatic spool filament impeller which when applied to vegetation trimmers does not waste filament and is simple, easy to use, consistent, reliable, and inexpensive. An automatic spool filament impeller having features of the present invention comprises a spool of diameter appropriate to extend a desired length of a filament made of a material appropriate for the application, such that, as the filament extends tangentially from the rotating spool, the free distal end of the filament traces a circle of a desired radius about the spool""s axis of rotation; the filament having one end affixed to the spool; the spool affixed to a means for rotating the spool.
The method of manufacturing an automatic spool filament impeller having features of this invention comprises the steps of determining the radius or diameter of a desired circular area or cutting swath to be defined by a distal tip of an extended length of filament rotating about an axis; selecting a filament of a material appropriate for the application; using the desired cutting swath diameter and characteristics of the selected filament to determine the ideal radius range of the spool; manufacturing a spool having the desired characteristic radius; winding a length of the selected filament about the manufactured spool of predetermined diameter; and affixing the spool to a means for rotating the spool at a speed sufficient to achieve and maintain the desired tangential extension of the filament about the spool when it is rotating.
The term filament, as used throughout this specification, is understood to comprise: a monofilament length of material; a multi-filament length of material; a poly-filament length of material; concatenated segments forming a length of material; and any other variation of a length of material having an application appropriate cross-section and is made of material capable of performing the desired function in conjunction with the automatic spool filament impeller. The word filament also incudes a combination of any of the above.
The term material comprises natural or man-made; metallic or not metallic materials. Example types of filament comprise: beaded or linked chain; wire; fiber optic thread or cable; monofilament or multi-filament thread; yam; string; tape; ribbon; tow; rope; cord; music wire; and cable any of which may be made using one or a combination of: pure metals, metal alloys, steel, brass, boron, quartz, carbon, glass, ceramic, cotton, wool, silk, flax, hemp, elastomers, polymers, plastics, nylon, rayon, Kevlar(trademark), spider silk, or Teflon(trademark)
Some versions of the present invention use more than one filament and/or more than one filament type depending on the application. Selection of filament type and number is made taking into account the device in conjunction with which the automatic spool filament impeller will be used and the particular application of that device. Various example applications of the automatic spool filament impeller are presented in this specification.
One advantage of applying this invention is that a reeling mechanism for retracting or extending a length of filament is unnecessary. The rotating spool impeller makes constant adjustments to maintain a cutting swath of a prescribed, unvarying size. If a portion of the extended filament breaks off, the remaining portion of extended filament increases its rotation speed relative to the rotating speed of the spool such that it unwinds the precise amount of filament necessary to restore the extended filament (and thereby the cutting swath) to the correct size. If the extended filament portion is too long, the extended filament""s rotating speed decreases relative to the rotating speed of the spool thereby rewinding just enough filament to restore the extended filament (and thereby the cutting swath) to the correct size. When the extended filament is of the correct length, the automatic spool filament impeller system is in equilibrium and the portion of filament which is extended is neither increased nor decreased because the rotational speed of the filament distal end is substantially equal to the rotational speed of the spool.
Applying the present invention to a vegetation trimmer, one can see that the size of the cutting swath is governed by centrifugal force and drag acting directly on the extended filament. If the extended filament is too long, drag overcomes centrifugal force and the extended filament rewinds. If the extended filament is too short, centrifugal force overcomes drag and the extended filament unwinds. If the extended filament is correct, drag and centrifugal force balance. Any deviation, large or small, is quickly compensated by the rewinding or unwinding of the precise amount of filament to restore the vegetation trimmer""s desired cutting swath.
The needs for a separate automatic or semiautomatic spool/filament advancing mechanism and a filament length monitoring mechanism are eliminated. The spool impeller cannot deploy an extended filament of excessive length, so the commonly used cutoff blade (to prevent overloading the trimmer motor) is eliminated. The automatic spool filament impeller is easy to reload, no disassembly or tools are required. In addition to the advantage of dispensing with the above described mechanisms, the present invention also offers the following advantages: there is no special spool housing required, and the spool impeller is directly affixed to the drive shaft. As a result of reducing the required number of parts: weight and cost are reduced while ease of use, maneuverability, and reliability are improved.
The automatic spool impeller of the present invention, when used as part of a fully automatic vegetation trimmer cutting head, improves the performance of the automated vegetation trimmer and is simpler, lighter, and less expensive to manufacture, operate and maintain. There is no need for the operator to monitor the filament as with prior manual and semiautomatic cutting heads. Periodic sudden increases in the size of the cutting swath and the resulting wasteful consumption of filament characteristic of prior automatic vegetation trimmer cutting heads are eliminated.
The vegetation trimming application is just one of many possible applications. The automatic spool filament impeller invention is useful for any process involving a whirling filament that is consumed. Examples include the mixing of fluids, paint and rust removal, cleaning smokestacks, debarking logs, staple fiber production and other applications described in this specification. There are many other applications.
It is therefore the object of the present invention to provide an automatic spool impeller for use in applications benefiting from continuously adjusting a rotating filament, centrifugally extended such that a constant extended filament length is maintained.
It is another object of the present invention to provide a fully automatic spool filament impeller for use in vegetation trimmers.
It is a further object of the present invention to provide an automatic spool filament impeller that reduces wasted operator time in non-trimming operations.
It is a further object of the present invention to provide an automatic spool filament impeller that minimizes wasting the operator""s time by reducing preparation for operation.
It is a further object of the present invention to provide an automatic spool filament impeller that minimizes wasting the operator""s time in repair operations.
It is a further object of the present invention to provide an automatic spool filament impeller that conserves filament.
It is a further object of the present invention to provide an automatic spool filament impeller that automatically maintains a consistent and predictable perimeter inscribed by the distal end of the filament extended during operation of the spool rotating at some predetermined speed.
It is a further object of the present invention to provide an automatic spool filament impeller that maintains a consistent and predictable cutting swath.
It is a further object of the present invention to provide an automatic spool filament impeller that has a simplified design to reduce manufacturing cost.
It is a further object of the present invention to provide an automatic spool filament impeller that has a simplified design to improve reliability and reduce maintenance cost.
It is a further object of the present invention to provide an automatic spool filament impeller that is lightweight.
It is a further object of the present invention to provide an automatic spool filament impeller that is simple to operate.
It is a further object of the present invention to provide an automatic spool filament impeller that is simple to reload.
It is a further object of the present invention to provide an automatic spool filament impeller that unravels as necessary but does not unravel easily otherwise.
It is a further object of the present invention to provide an automatic spool filament impeller that is useful for any process involving a whirling filament that is consumed.
It is a further object of the present invention to provide an automatic spool filament impeller that is useful for mixing fluids.
It is a further object of the present invention to provide an automatic spool filament impeller that is useful for paint and rust removal.
It is a further object of the present invention to provide an automatic spool filament impeller that is useful for cleaning smokestacks.
It is a further object of the present invention to provide an automatic spool filament impeller that is useful for debarking logs.
It is a further object of the present invention to provide an automatic spool filament impeller that is useful for staple fiber production.
Other and further objects of the present invention will become apparent from a reading of the following description taken in conjunction with the appended claims.
In order to meet the foregoing objectives and to overcome the problems inherent in the prior art devices, the present invention provides a method and apparatus for an automatic spool filament impeller for use in applications benefiting from continuously adjusting a rotating filament attached at one end to a rotating spool, the filament centrifugally extended such that a constant extended filament length is maintained.
In one form of the invention, an automatic spool filament impeller having features of the present invention comprises a spool of a diameter appropriate to extend a desired length of a filament made of a material appropriate for the application, such that, as the filament extends tangentially from the rotating spool, the free distal end of the filament traces a circle of a desired radius about the spool""s axis of rotation; the filament having one end affixed to the spool; the spool affixed to a means for rotating the spool.
In another form of the invention, the above described automatic spool filament impeller is operationally combined with a vegetation trimmer.
In another form of the invention, a method for manufacturing an automatic spool filament impeller having features of this invention, comprises the steps of: determining the radius or diameter of a desired circular area or cutting swath to be defined by a distal tip of an extended length of filament rotating about an axis; selecting a filament of a material appropriate for the application; using the desired cutting swath diameter and characteristics of the selected filament to determine the ideal radius range of the spool; manufacturing a spool having the desired characteristic radius; winding a length of the selected filament about the manufactured spool of a predetermined diameter; and affixing the spool to a means for rotating the spool at a speed sufficient to achieve and maintain the desired tangential extension of the filament at a point on the spool""s cylindrical surface when the spool is rotating.